Too much light, especially blue light, less than two hours before bed overstimulates the pineal gland, that normally produces melatonin at night. Melatonin helps one to sleep and helps to cleanse and rebuild the body while one sleeps.
Lack of socialization and empathy. Impaired ability to self-heal. School systems, like the Worcester Public Schools, have banned the use of cell phones due to the negative effects on behavior and attention span of students.
Apps and websites are engineered to maximize the time spent on them, according to Tristan Harris,an app developer who found himself checking his phone compulsively and founded a company that was bought up by Google. Ramsey Brown says using a continuous scrool is a way for Facebook and other sites to keep you looking at them. Psychologist Larry Rosen says the apps exploit the generation of cortisol in the body that creates anxiety if one has not checked their phone in a while. When one is interrupted it takes twenty minutes to get back on track. Dave Zickerman has worked on making sites and apps as engaging and appealing as possible by employing "gamification" techniques. Ramsey Brown of Dopamine labs has now developed an app to give users twelve seconds of Zen before launching any app, the idea of giving one "space" but this was, at first, rejected as unacceptable by the Apple Store because of encouraging one to be less hooked on their phone. Apple relented after the 60 Minutes story ran. 
790 WiFi Dangers Episode 4: Impacts of Excessive Screen Time, Cecelia Doucette, Nov 20, 2016